The present invention relates to a chuck for supporting a device under test (DUT) in a probe station and, more particularly, to a chuck adapted to testing electrical and optical properties of a DUT at a temperature other than the ambient temperature.
Many electrical devices, in particular semiconductor based devices, include both electrical components and optical components. Some electro-optical devices receive an optical signal from an optical source and convert the received optical signal into an electrical signal, e.g., a photo-detector. Other electro-optical devices convert an electrical signal into an optical signal, e.g., a light-emitting-diode. Yet other electro-optical devices may include multiple optical and/or electrical components. A probe station may be used to characterize the operation of these devices.
In a probe station, an electrical device-under-test (DUT) is commonly supported on and restrained to the upper surface a chuck while probes are positioned above test pads on the upper surface of the DUT and then brought into contact with the test pads during measurement of the device's operating parameters. The chuck is usually supported on a movable stage permitting movement the chuck to facilitate aligning the probes with the test pads of the DUT. However, an electro-optical device commonly includes electrical connections on a first surface of the device and optical input or output at another surface of the device. For example, an optical signal from a light source may be directed toward the DUT from below, above, or to the side of the DUT while a probe or connector on the upper surface is used to sense the resulting electrical output from the DUT. Similarly for example, a probe or connector may be used to provide an electrical excitation at the upper surface of the DUT while an optical sensor located below, above, or to the side of the DUT is used to sense the resulting optical output.
An optical chuck may used in a probe station to support a DUT that requires an optically accessible path to a surface of the DUT that is normally blocked by the chuck. Harris et al., Patent Application Publication, Pub. No.: US 2003/0042889 A1, incorporated herein by reference, disclose an optical chuck that includes a central, optically transparent medium over which the DUT is supported to provide an optically accessible path to all sides of the DUT. The DUT and the optically transparent medium are supported above a base by a plurality of columnar supports permitting an optical transducer to be located below the transparent window to either sense optical output from the DUT or transmit optical signals to the DUT from below.
While an optical chuck provides an access path for optical signals to or from a DUT, it is often desired to test these devices at a temperature other than the ambient temperature. Thermal chucks are commonly used for testing electrical DUTs at elevated or depressed temperatures. A thermal chuck typically includes a heat source to raise the temperature of the surface of the chuck supporting the DUT and, as a result, the temperature of the DUT. Typically, probe station thermal chucks are heated by thermoelectric devices that rely on the Peltier effect or wire resistance heaters. However, these devices are optically opaque and would interfere with an optical path to the DUT if used to modify the temperature of an optical chuck.
What is desired, therefore, is a thermal optical chuck for use in a probe station that permits a DUT supported on a surface of the chuck to be tested at a temperature other than ambient while providing optical access to the underside the DUT.